Wherever there is the need for a security system, there is also a need for sensing devices which will indicate when a barrier has been comprised. In specific instances where the barrier is a door or a gate, it may be important to known when the barrier is even slightly ajar. An ability to detect even the slightest opening of a door or gate is of obvious importance in bank buildings, financial instutitions, prison, and correctional facilities.
In order to be effective as part of a security system, a door position indicator must be extremely sensitive to changes in the configuration of the door. Indeed, a door which can be even slightly opened without alarming the system may allow deactivation of the door position indicator to permit an undected further opening of the door. Consequently, sensitivity of the door position indicator is crucial to the effectiveness of the security system. Further, it is important that the door position indicator be concealed and tamper resistant for security purposes. Additionally, it is important that the door position indicator be easily adjusted, even subsequent to its installation, to maintain the sensitivity of the indicator.
Several examples of door position indicators can be given. For example, U.S. Pat. No. 3,806,852 to Suska discloses a switch activating hinge which relies on the juxtaposition of the hinge leaves for a door closed indication. Somewhat differently, U.S. Pat. No. 3,838,234 to Peterson discloses an interrupt electrical circuit which is activated by mechanisms held in the knuckles of the door hinge to indicate whether the door is closed or open. U.S. Pat. No. 4,049,934 to newlon, like the Peterson patent, discloses a device held in knuckles of the hinge. The Newlon patent, however, discloses an adjustable component for its security hinge. None of these devices, however, are able to be readjusted after some misalignment of its mechanism while the door remains operable.
The present invention recognizes that an extremely sensitive door position indicator is needed to provide effective security. Further, the present invention recognizes this sensitivity can be disturbed to give erroneous indications at any time after installation. Thus, there is a need for the ability to easily adjust the indicator back into its proper working configuration, without dismantling the door, even though the maladjustment occurs after the door has been installed.
In light of the above, it is an object of the present invention to provide a door position indicator which is very sensitive to the condition of the door whether it be open, closed or merely ajar. Another object of the present invention is to provide a door position indicator which is adjustable to maintain proper door position indications even after the door has been installed. Still another object of the present invention is to provide a door position indicator that is concealed from view and substantially tamper resistant. Yet another object of the present invention is to provide a door position indicator that is relatively easy to install and operate, relatively simple to manufacture and comparatively cost effective.